Tyre Pressure & Fuel Economy

[bfi2906]

I've just hit 2000k's - so Woo Hoo for that.

I'm interested in experiences around what fuel economy people are getting. I know one doesn't buy a 135 with fuel economy as a high priority, but reading the various threads here and in the general forum, I get the sense that the 11.4l/100k's (all city driving) is higher than others are getting. I haven't reset it since new.

I checked the tyre pressure for the first time since delivery, and cold, it was 50psi (so much for the 40psi max on the sidewall of the tyres). So I don't think that's having a negative effect on the economy.

Will the economy start to get better now that it's got a few K's on it. If so, what's reasonable milage around town.

Finally, I'm driving from Sydney to Armidale this week, what tyre pressure is ideal? There'll only be my wife and I and a couple of light items.

Cheers,
B.

[x5mad]

50PSI??? YIKES!!!

Your risk of blowout and damaging your rims if you hit a pot hole is greatly increased.

You should drop it as soon as possible to maufacturer recommendations. I find however that 36psi all round works well.

50psi is the pressure they use whilst transporting the car and whilst in storage.

I think most tyres have max pressure rating of 51psi (the 40psi max you are reading has to do with the max pressure the tyre shop is allowed to put in it whilst mounting the trye).


I am getting about 12l/100 at the moment but do drive on occasion with a lead foot. Economy will definately improve the more you have run in your car, I started seeing it around 6000km onwards.

But definately change those pressures soon as the longer you leave it the higher the risk of ruining your tyres, as like all things elastic they have ''memory''. So if you leave it a long time and reduce pressure in say 6 months then it may be too late, as warm you may be approaching 58psi at which point its past or approaching its elasticity and together with sidewall flexing etc even if you reduce pressure at a later stage it will be too late, the tyre will be a hazard.

[d3syd]

I would follow BMW's recommended tyre pressure. I never trust dealers to get the correct pressure. My car has done 14,000 kms and it has settled on 10.1 - 10.2 l/100km. I mostly do country driving, albeit often with a heavy foot at lots of corner carving....

[takahashi]

Not only 50psi will wear out the centre of the tyres, it reduces traction and your tyre not able to get enough heat in cold days.

I have 40 psi in my tyres and I have 14L/100km. The traffic is bad in Melbourne and I only do short trips. I found the car uses a lot of fuel when cold.

[bfi2906]

Thanks for the replies.

So much for the $1600 car wash they call pre delivery. Kinda makes all the talk from dealers to justify that cost a bit of a laugh. If they can't even be bothered to check the tyre pressure, makes me wonder what else they couldn't be bothered to do. What a rort!

I have dropped the pressure to 38(F) & 36(R). So all good there.

Sounds like my fuel economy is within expectation for the circumstances.

Any other views welcome.

Thanks again.

[MikeVictor]

Usually 700km of city driving with about 300km of highway driving a month for me, tyres set to 36PSI all-round. Avg consumption is 11.2L/100KM.

Coming home from Montville yesterday on the Bruce Hway I checked the "live" consumption and it was around 5.5L/100KM.

[Zuzu]

Still averaging about 11.4 with about 40% city and the rest highway..13K Km's on the dial.

[MickyD]

haven't checked my pressures yet, averagine 5.1L/100k's, but then it's not a 135

[amk2912]

Used to run 37psi front and rear on the 135i with an average of 10.6L/100km. By comparo the M3 is averaging 13.0L/100km.

[05C4R]

check your steering and wheel alignment before you put to many k's on it as well. the bastards don't do wheel alignments at all yet they say they do. and if your tyres had 50psi in them you definately did not get a wheel alignment. just cos bmw have prestige doesn't mean they are any better then a used car salesmen on parramatta rd.

28psi in my tyres works a dream and i get 10.4 after doing 15000k

[Kris]

What do people run when using 225/40 front, 255/35 rear?

[x5mad]

36 all round

[MikeVictor]

Originally Posted by Kris

What do people run when using 225/40 front, 255/35 rear?

Same, 36 all round.

[Guran]

I usually use 38psi in my tyres and reading this thread realised that's been a while since I checked. A quick visit to the garage and they're at 30psi cold. The recommended placard pressure is 38psi/260kPa front and rear for the stock 215/40R18 front and 245/35R18 rear (44psi/300kPa rear with full load). So I'll be stopping by the nearest servo before my next punt.

BTW, with 8800km on the clock, my average is 10.8L/100km calculated from fill volumes and odometer readings (not the OBC). The best I've seen is 9.2L/100km on a long freeway trip, and the worst is 12.7L/100km after a "spirited" drive.

[oneill3]

I've almost got 2000km on the clock. All city driving. I've averaging about 16L-17L/100K.

I just don't understand why my fuel usage is so high

['fatboy']

11.2l/100km and about 37-38psi all round - done 6,500kms. Mix of city and hwyway k's

It's been slowly creeping from about 10.5l/100km but I'm probably exploring the limits more frequently

[Taymaishu]

Quite interesting discussion....

I'm running 28 PSI front, 32 Rear on my WRX.

Mind you, that's also an AWD car, and most of the force (under breaks or acceleration) around a corner is on the front outer tyre - so the lower pressure creates a hell of a lot more grip (and wear on the inside of the front tyres!)

I had a blowout on the M2 @ 110km/h back in March. The front left went. It was a struggle to get the car under control and eventually used the handbrake at 50km/h to get the tail back aligned in the breakdown bay.

It turned out that tyre rotations on AWD Subaru's is so hard to guage, you end up with bad, bad tyres. I had 40% tread on the outside of the tyres, and it was through to the metal core on the inside of BOTH tyres. The rears were perfect. There was a lovely strip running around the very inside of the flat of both front tyres where the metal core was sticking out.

Very lucky

[dk130i]

Originally Posted by Taymaishu

Quite interesting discussion....

I'm running 28 PSI front, 32 Rear on my WRX.

Mind you, that's also an AWD car, and most of the force (under breaks or acceleration) around a corner is on the front outer tyre - so the lower pressure creates a hell of a lot more grip (and wear on the inside of the front tyres!)

In my experience (2 previous subarus) AWD cars with standard alignment and correct pressures tend to wear the outside corners not insides. Could your tyre wear be attributed to excessive negative camber? Is your car lowered?(this usually increases negative camber)
Lower pressures generally mean excessive wear on both inside and outside corners.

[Taymaishu]

Originally Posted by dk130i

In my experience (2 previous subarus) AWD cars with standard alignment and correct pressures tend to wear the outside corners not insides. Could your tyre wear be attributed to excessive negative camber? Is your car lowered?(this usually increases negative camber)
Lower pressures generally mean excessive wear on both inside and outside corners.

Had a wheel alignment check (and toe/hell camber check) just before Christmas before i drove to Queensland.

Last service - all fine.

The wear was crystal clear - completely on the inside of the front tyres.

She hasn't been lowered and the camber (as checked) is perfect. I always note how the wheels look from behind - and nothing is different at all.

I do fang it around corners, more than the average WRX driver, but i don't do anything much on top of that.

Any other clues?

[sparoz]

Originally Posted by mattyv

Usually 700km of city driving with about 300km of highway driving a month for me, tyres set to 36PSI all-round. Avg consumption is 11.2L/100KM.

Coming home from Montville yesterday on the Bruce Hway I checked the "live" consumption and it was around 5.5L/100KM.

That's right i was supposed to spot your car!

Mine was set up 36/34 - avg = 10.1L/100KM. I guess I always have that stretch of highway going to and from work. Probably thinking about increase to 37/34 next time round.

[dk130i]

Originally Posted by Taymaishu

Any other clues?

Nope!

Sorry, I am not really qualified, talking purely based on my observations.(some may say out of my arse)

[Taymaishu]

Originally Posted by dk130i

Nope!

Sorry, I am not really qualified, talking purely based on my observations.(some may say out of my arse)

Oh well - she's going to be sold very soon (I do hope).

What's the wear pattern on the BMW's?

Considering the "50/50 weight distribution" i imagine it would be a little different from other RWDs.

Having said that, it's going to be the first R/FWD i've ever driven.. When i was on my P's i sometimes drove a VT Holden Wagon (suitably nicknamed the "Whale"), and ended up spinning the rears very often..